The filtration and fouling performance of membranes with different pore sizes in algae harvesting

In this study, ultrafiltration membranes with three different pore sizes were applied for algae harvesting to investigate filtration performance. The critical fluxes (J_C) increased as the pore size increased, and the J_C of 0.03-, 0.05- and 0.1-μm membranes were 20.0, 25.0 and 42.0Lm^-2h^-1, respectively. During continuous filtration, 0.7J_C was selected as the operation flux and the 0.1-μm membrane had the highest initial flux and final flux. It also had the highest flux decline rate, and therefore, the 0.1-μm membrane was more appropriate for algae separation compared to the 0.03- and 0.05-μm membrane. The mechanism by which pore size influenced filtration performance and membrane fouling was presented from the viewpoint of permeate drag force (F_D). A lower F_D retarded the velocity of algae cells towards the membrane, which could decelerate the deposition of particles on the membrane and thus reduce the membrane fouling rate. As the pore size increased, the membrane hydraulic resistance (R_m) decreased, which led to a decrease of F_D.